Some experimental observation on the toxicity of urea to sheep

Abstract

The rumen pH and ammonia nitrogen levels were recorded in sheep fed on different amounts of urea in different ways. It was found that when the urea was sprayed onto the daily intake of roughage these levels remained low, even when intakes of 100 g urea were obtained, compared with the levels recorded when lower levels of urea (25 g) were given as a drench. As the rumen pH level rose to 7.0 and above, the periods of time spent ruminating declined until at about a pH of 7.3 complete rumen stasis occurred. The stasis did not occur at higher levels of rumen ammonia nitrogen provided that the pH level was kept down. Sheep readily consumed large amounts (up to 100 g) of urea per day provided that the concentration of urea in the ration did not exceed 6 per cent.; when this happened the food intakes were markedly reduced. A theoretical explanation is offered of the influence of the rumen pH level on the rate of ammonia absorption from the rumen.